Motor-control system.



'J. H. HALL.

MOTOR CONTROL SYSTEM. APPLICATICN FILED Dcm 1941...

1 275,909 I Patented Aug. 13, 1918.

m :C W 1? ya u //4// f7 n ggi I N? A TT ORNE Y.

UNITED srAr s JAYH. HALL, OF CLEVELAND, OHIO, ASSIGNOES TU THE ELECTRIC CQNTSROLL' MANUFACTURING COMPANY, OF CLEVELAND, QHIO, CGRPGERATIGET 53E MOTOR-CONTROL SYSTEM.

Specification of Letters Patent.

Application filed December 7, 191?. Serial .Jio. :lfififlt-S.

To all whom it may concern: r

' Be it known that I, JAY H. HALL, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented new and useful Improvements in MotorControl Systems, of which the following is a specification.

This invention relates to motor control systems, and particularly to control systems for motors having shunt wound fields, in which the speed of the motor may he increased or decreased at will by varying the field strength.

In motor control systems of this class an adjustable resistance is usually provided to vary the field strength of the motor. If, during the operation of the motor, this field resistance be changed by a large increment to give a correspondingly large variation or" speed, the sudden change in field strength wlll cause a dangerously large fluctuation or speed. 1

- In the accompanying drawing, Figures 1, 2, ,3, and 4 are diagrams of motor control systems, showing four of the many forms in which my invention may be embodied.

' Referring to Fig. l, A represents the motor armature, F its shunt field, R is a speed-regulating rheostat, B an adjustable field resistance, and S and S electromagnetic switches. A winding W on the switch. S and a winding W on the switch S are connected in series with the armature A. across the positive and negative supply mains P and N. The switch S has also a shunt winding W wound to oppose the winding N and connected directly across the mains and N. The switch S is normally open and upon closing shortcircuits the regulating rheostat R The switch S is normally closed, and upon opening inserts the resistance R in the field circuit, The field circuit may be traced from the positive mainP 'throughthe regulating rheostat R (or through the contacts of the switch S if .of the switches may he termined Values.

Fig. l is as follows: Suppose the to weaken the field'and i.

switch to open again.

. set, and the switch S opening and osition. Durin this oneratiou the same time, according send tacts of the switch i, tive main. Each oft with an ad usta-ble opera ti which the operating currei'it The 0 eration of the s stem ture A is rotating at a cert running curr oi the motor is predetermined current Val e neee close the switch S Theswitch. S r hecause'ot the opposition of its win It now the speed regulating rheostat. moved to insert resistance in the i the motor, an excessive current nu upon flow in the armature circuit a the switch S shert cireuiting the R and streng hening strength. mmediately thereupon rent in the armature decreases, ca.

This act on tinues the armature gradually new speedier which the rheostat r and finally coming to rest again in S has remained closed.

' If it be desired to decrease the motor, the rheostat "i is moved. resistance and strengthen the l motor will thereupon act reversing the direction of the c armature and in the vii-n t n The windings "W other, causing the switch t ns later, the switch S the resis ice R be of a suitable amonn e field he weakened by the opening or theswitc notwithstanding that rheostat short-circuited by the switch. S armature current will he d weakened field. e upon close again. '1. his Z'tQhiUfl. switch. 5* opening closing armature slows down to the spec; which the rheostat R was adjusted. I motor reaches approximately this new speed,

the armature current and hence the current in the winding W reverses to its ori inel normal direction, and the, two winoin.gs of 1:1

cuited,

the switch S again oppose each other and the switch S remains closed.

lfluring the operation of the switch S as just described, the corresponding action of switch 8 will depend upon the relative operating current values of the switches S and 3 which may be adjusted by adjusting the number of turns in the windin s W and it, or y adjusting the relative'engths of the air gaps M or by any other suitable adjusting means. llhus, by suitable adjustments, the switch S may be made to remain closed throughout the opening and closing operation of the switch S in which case resistance B may be made relatively iargc to compensate for the short-eircuited rheostat R or by other adjustments switch may be made to vibrate in unison with the switch S or by other adjustments the switch S may remain open during the operation of the switch S in which case the re ance R may be made relatively small, since it will not he conjunction with the resistance of the rheostat R".

In the system shown in Fig. 2, the winding it oi the switch S is wound to oppose the win ding W as in Fig. 1, but is not permanently connected across the supply mains, in that figure. One terminal of the winch ing it is connected directly to the supply main N and the other to thesupply main P through the contacts of the switch S and hence the winding W does not receive current until the switch S closes, To prevent the switch S from opening under the influence of the winding ll alone and before the switch S has closed to energize the opposing nding W the winding W is given fewer *ns than the winding W of switch S he system of Fig. 2, the switch S is bly adjusted to remain closed during operation of the switch S in order to itain the energization of the winding" and to keep the rheostat R short-cirln the s stem shown in Fi 3 the switch 0 has only a shunt winding W connected across the armature terminals. The operation of the switch S while the speed of the mo is being increased, is the same as that During its operation the winding he switch 8* is energized by the vole across the armature terminals, this vol e being somewhat less than line voltage, ehy the energization of the winding is insufiicient to open the switch S "ing a reduction of the speed of the motor, however, while the motor is acting as a generator, the voltage on the winding V is somewhat greater than line voltage, and enthe winding W suiiiciently to open the switch S in other respects the operation. of the two switches in f is the same in Fig. 1.

system shown in Fig. a is the same as shown in Fig. 3, except that the winding W of the switch S is not permanently connected across the armature terminals, but is so connected through the contacts of the switch 8 when it is closed. Preferably the switch S is adjusted to remain closed during the operation of the switch S in order to maintain the energization of the winding W and to keep the rheostat R short-circuited.

In each of the systems above shown and described, it will be seen that when the speed-regulating rheostat is adjusted to vary the motor speed, any tendency of the armature current to rise to excessive values is offset by the action of the switches S and S which vibrate or flutter on their contacts to alternately cut in and cut out field circuit resistance, thereby keeping the armature current within predetermined limits.

Other systems than those shown and described may be made, employing my invention, and the scope of my invention is, therefore, not limited to the exact systems disclosed.

I claim 1. In a motor control system, a motor, a shunt field circuit therefor, a variable speedchanging resistance and a fixed resistance in the field circuit, a switch for cutting the variable resistance out of and into the field cut-ting the fixed resistance into and out of the field circuit to decrease the speed of the motor when the rheostat is moved to a decreased speed position.

3. In a motor control system, a motor, a shunt field circuit therefor, a variable speedchanging resistance and a fixed resistance in the field circuit, a switch for cutting the variable resistance out of and into the field circuit to increase the speed of the motor when the variable resistance is increased, and a switch for cutting the fixed resistance into and out of the field circuit to decrease the speed of the motor when the variable resistance is decreased.

4. In a motor control system, a source of supply voltage, a motor, a motor circuit and a shunt field circuit therefor, a variable speed-changing resistance and a fixed resist ance in the field circuit, a switch for cutting the variable resistance out of and into the field circuit to increase the speed of the morasse tor and responding to the main motor current, and a switch for cuttin the fixed resistance into and out of the eld circuit to redr ce the speed of the motor and respondin to electrical conditions of the motor circult caused by the greater-than-source voltage at the motor terminals during the slowing down of the motor.

5. In a motor control system, a source of supply voltage, a motor, a motor circuit and a shunt field circuit therefor, a speed changing rheostat and a fixed resistance in the field circuit, a switch for cutting the rheostat out of and into the field circu1t to increase the speed of the motor when the rheostat is moved to an increased speed position and responding to the main motor current, and a switch for cutting the fixed resistance into and out of the field circuit to decrease the speed of the motor when the rheostat is moved to a decreased speed osition and responding to electrical conditlons of the motor circuit caused by the greater-than-source voltage at the motor terminals during the slowing down of the motor. 1

6. In a motor control system, a source of supply volta e, a motor, a motor circuit and a shunt fiel circuit therefor, a variable speed changin resistance and afixed resistance in the fie d circuit, a switch for cutting the variable resistance out of and into the field circuit to increase the speed of the motor when the variable resistance is increased and responding to the main motor current, and a switch for cutting the fixed resistance into and out of the field circuit to decrease I the speed of the motor when the variable resistance is decreased and responding to electrical conditions of the motor circuit caused by the greater-than-source voltage at the motor terminals during the slowing down of the motor.

7. In a motor control system, a source of supply voltage, a motor, a motor circuit and a shunt field circuit therefor, a variable speed-changing resistance and a fixed resistance in the field circuit, a switch for cutting the variable resistance out of and into the field circuit to increase the speed of the motor and respondin to the main motor current, and a secon switch for cuttingpthe fixed resistance into and out of the field circuit to reduce the speed of the motor and responding, only when the first switch is closed to electrical conditions of the motor circuit caused by the greater-than-source voltage at the motor terminals during the slowing down of the motor.

8. In a motor control system, a source of supply voltage, a motor, a motor circuit and a shunt field circuit therefor, a speed changing rheostat and a fixed resistance in the field circuit, a switch for cutting the rheostat out of and into the field circuit to increase the speed of the motor when the rheostat is moved to an increased speed pospeed changing resistance and a fixed resistance in the field circuit, a switch for cutting the variable resistance out of and into the field circuit to increase the speed of the mo-- tor when the variable resistance is increased and responding to the main motor current, and a second switch for cutting the fixed resistance into and out of the field circuit to decrease the speed of the motor when the variable resistance is decreased and responding only when the first switch is closed to electrical conditions of the motor circuit caused by the greater-than-source voltage at the motor terminals during the slowing down of the motor.

Signed at Cleveland, Ohio, this 3rd day of December, 1917.

-JAY HALL. 

